Thermoelectric generator



@411 Iii 14-3. W. A. RAY

THERMOELECTRIC GENERATOR Filed June 17, 1940- A ANEY' QNVENTQ R, Mom; K4

wan a. Glen 1e. cam Application June 17, 19a, Serial No. 341,005

2 Qlalms.

This invention relates to a thermoelectric generator. The principles ofthennoelectricityare now well understood; it is necessary merely tostate that when conductors made from dissimilar metals or alloys arejoined together, and heat applied to the junction, an electric currentis generated. This current is a function of the temperature difierential between this hot junction" and the "cold junctions" where thefree ends of the conductors are joined to a circuit. It has and thephysical proportions of the elements may be chosen to comply with thedesired characteristics of the thermopile.

It is one of the objects of this invention to provide a simple, compactand inexpensive thermoelectric device.

The hot junctions of a thermopile may be heated in any convenientmanner, but in order to make it possible to install the device near anydesired location, this invention contemplates the use of electric poweras the source of heat. It is accordingly another object of thisinvention to provide an electrically heated thermopile, and preferablyone arranged to be inserted in an ordinary socket outlet such as isencountered in commercial lighting circuits. I

Thermoelectric devices of this character may be conveniently utilized asa source of low voltage direct current energy for operating controlapparatus, such as are needed for example in heating and ventilatingsystems.

This invention possesses many other advantages, and has other objectswhich may be made more easily apparent from a consideration of oneembodiment of the invention. For this purpose there is shown a form inthe drawing accompanying and forming part of the present specification.This form will now be described in detail, illustrating the generalprinciples of the invention; but it is to be understood that thisdetailed description is not to be taken in a limiting since the scope ofthis invention is best defined by the appended claims.

Referring to the drawing:

Figure l is a sectional view, drawn on an enlarged scale, of anembodiment of the invention;

sense,

Fig. 2 is a sectional view taken along plane 2--2 of Fig. 1;

Fig. 3 is a pictorial view of elements of a heating unit, used inconnection with the invention, the parts being shown separated, and oneof the parts being shown in partial section;

Fig. 4 is a pictorial view of a cover member adapted to be used inconnection with the invention;

Fig. 5 is a pictorial view of be utilized with the invention;

Fig. 6 is a greatly enlarged end view of a hot junction of one of thethermocouples utilized with the invention;

Fig. 7 is a greatly enlarged sectional view taken along plane 1-'! ofFig. 6; and

Fig. 8 is a wiring diagram illustrating the mode of use of thethermocouple device.

In the present instance the thermoelectric genorator is shown asincluding a plurality of ther-- mocouples to form a thermopile. As showndiagrammatically in Fig. 8, these thermocouple structures are shown asconnected in series to operate a load I; the number of thermocouplesbeing a matter of choice. The thermocouples are formed by the pairs ofconductors 2-9, fl-i, E'l, 89 and iU-J I. Each of the thermocouples isformed of dissimilar metals as heretofore explained; for example,Chrome! and Copel. They are joined in series as illustrated more clearlyin Fig. 8, the lower junctions l2, Ii, M, Ii and I6 forming the hotjunctions. The upper junctions l7, l8, l9 and 26 form the coldjunctions. The conductors 2 and II form the terminal conductors.

As shown most clearly in Figs. 1, 6 and '7, the junctions may beconveniently formed by twisting the ends of the respective conductorstogether; and if desired by joining them more permanently as by weldingor fusion.

In the present instance the thermocouple conductors 2 to II inclusiveare shown as passing through a cover memberzi (Figs. 1 and 4). Thiscover H is preferably made from a refractory insulation material such asporcelain or the like. To accommodate the thermocouple conductors thecover 2| is shown as having the pairs of apertures 22, 2t. 2t, 25 and26.

The hot junctions I2 to Hi inclusive are shown as extending into thehollow space 21 of a hol low body 28. This hollow body it is alsopreferably made of a refractory insulation material such as porcelain.These hot junctions are thus disposed in an annular fashion about theaxis of the body it which is of generally cylindrical a. cap adapted toform. The cover member 2| serves to enclose the hollow space i! and isheld in closed relation in a manner to be hereinafter described.

Heat is radiated to the annularly arranged hot junctions ii to 86inclusive from an electric heating unit 29. This heating unit is shownas supported at the bottom of the space 27. It

comprises a coil of wire til (Figs. 1 and 3) disposed around arefractory cylindrical hollow insulation support 31. The conductor 30may be made from nichrome or other electrical heating wire. Itsterminals may be connected to the conducting top and bottom washers 32and it.

In order to support the heating unit is in a substantially centralposition with respect to the hot junctions of the thermocouples asupporting post (it is utilized. This post passes centrally through thebody 3|. It conveniently takes the form oi a flat head screw with thethreaded end extending above the heating unit it. The screw it may passthrough a terminal Washer 35 disposed on the outside of the lower end itof the supporting body 28. In order that the post it may securely holdthe heating unit 29 in place, the body 28 is provided with a recess 3'!in the end portion 36, and in communication with the space 21. In thisrecess is set a supporting cup it of conducting material. The heatingunit support 3| seats within the cup. By the aid of the washer iii anelectrical connection is made from the lower terminal of the wire it tothe cup it.

At the upper end of the heating unit iii a conducting flanged washer es(Figs. 1 and 3) is provided. The flange of this washer overlies thewasher 32 and provides an electrical connectlon to the upper terminal ofthe wire it. The post id passes through the washer iii and the nut itholds the assembly together.-

The connections to the electrical heating unit is may be readily made bythe aid of an ordinary screw socket outlet of a commercial electricsupply system, or the like. For this purpose the lower portion of thebody it is provided with the helical c rrugations ll. Over thesecorrugations is disposed a conventional form oi screw shell M, of copperor brass. This screw shell is shown as having a bottom flange iili forholding the shell in place. The body id furthermore has a recess itthrough which a connecting lead iii may pass to connect the cup iii withthe screw shell t2. The upper terminal of the wire til, being inelectrical connection with the post it is similarly in electricalconnection with the lower washer 35. The lower end it oi? the body ii ispurposely made of reduced size to simulate an ordinary plug that may bescrewed into a conventional electric socket. The washer it is adapted tocontact with one of the terminals of the socket, and the screw shell Mis adapted to cooperate with the corresponding screw shell forming theother terminal oi the soclret.

In this manner the thermoelectric device may be compactly andconveniently arranged (1 supported. It may be utilized wherever aterminal commercial socket is available.

The transfer of heat from the heating unit to the hot junctions isprovided mainly by radiation from the exposed radiating surfaces of thewire iii. In order to increase the absorption oi! radiated heat at thehot junctions, each of these hot junctions is provided with an absorbingmember exposing an extended absorbing surface to the radiated heat.Referring more particularly to Figs. 2, 6 and 'l, the heat absorbers mayasoaose be in the iorn'i oi extremely thin metal members lii, such metalfoil. Each of these at sorbers may be twisted or wrapped around thecorresponding hot junction as illustrated most clearly in Fig. 6. A tallportion extends substantially from one hot junction to the next one. Inthis way a substantially continuous absorbing surface is presented tothe radiated heat. The surface of the tinfoil absorbers tit: directedtoward the heating unit 2% is purposely made rough or mat or darkened inorder to facilitate the absorption of heat. Further, to ensure againstpossible short circuiting between the adjacent hot junctions by theabsorbers ii, a very thin sleeve ll of nonconducting material such asmica, may be interposed between the absorber it and the thermocouplejunction conductors. This very thin mica does not appreciable; retardtransfer of heat from the absorbers iii to the hot junctions. Thethickness of the foil forming the absorber it is exaggerated in Figs. 6and 7.

The terminal conductors 2 and H may be joined to appropriate bindingposts ill and M (Fig. 1). These binding posts ill and iii are shown inthis instance as supported by a metallic cap til shown to best advantagein Fig. 5. This metallic cap it has a depending flange iii which maytelescope over the periphery of the cover iii. The lower edge iii of theflange iii may be crimped over the sloping surface of a flange 5d formedintegral with the body iii. The cap til is thus secured to the body iii.In order to hold the cover it in place with respect to the cap till, theflange [ii is further provided with several upset portions iii adaptedto be turned inwardly in appropriate slots formed in the flange lit toengage the lower surface of the cover 2 i.

The hollow body it being closed by the cover ii, there is an assuranceagainst unnecessary dissipation of heat from within the hollow space iiof the body iii. The heating unit 29 acts efficiently to heat the hotjunctions.

The cold junctions Ill, Iii, iii and it being disposed outside oi thebody and within the cap fill may be lrept quite cool by being directlyexposed to the air. For this purpose the cap Ell is shown as providedwith a number of large ventilating apertures lit.

The mode of operation of the structure is quite clear from theforegoing. It may be screwed into any appropriate outlet socket. Theradiating heat produced by th heating unit it serves to elevate thetemperature of the hot junctions ii to it inclusive, as compared withthe tempera ture of the relatively cool junctions Ill to ill inclusive.Accordingly a load connected to the binding posts id and iii may besupplied with the desired low potential direct current energy.

What is claimed is:

i. In a thermoelectric generator, a hollow body open at one end, anelectric heating unit supported centrally oi the body and radiating heattoward-the walls of the body, a series of thermocouples having their hotjunctions interposed between the unit and the walls of the body. acentral conducting post extending into the body through the closed endof the body and electrically connected to one terminal of said unit, aconducting screw shell carried exteriorly of the body and connected tothe other terminal of said unit, said shell and post being adapted tocooperate with a plug socket to conduct electrical power to the unit, acover for the body, the conductors forming the couples passing throughsaint cover. and a cap disposed over the cover for nous:

ing the cold junctions, said cap having passages for circulation of airaround said cold junctions.

2. In a thermoelectric generator, a hollow body open at one end, anelectric heating unit in the form of a hollow coil supported centrallyof the 5 body, a series of thermocouples having their hot junctionsinterposed between the unit and the walls of the body, so as to beheated by said unit, a central conducting post passing through theclosed end of the body and into said coil and (damping said coil to thebody, said post having 10 time extend out of the body.

WILLIAM A. RAY.

